Various forms of building blocks heretofore have been provided with interlocking projections and recesses. However, most of these previously known forms of building blocks include mating projections and recesses which may be used to interlock only adjacent staggered courses of blocks and which are not operative to interlock stacked tiers of blocks while a quantity thereof are being stored or shipped in a compact state.
Examples of various different forms of building blocks including some of the general structural and operational features of this instant invention are disclosed in U.S. Pat. Nos. 86,961, 253,416, 779,613, 1,833,875, 2,062,851, 2,474,186 and 3,382,632.